1. Technical Field
The embodiments described herein relate to a semiconductor apparatus, and more particularly, to a data output driving circuit for a semiconductor apparatus.
2. Related Art
As shown in FIG. 1, a conventional data output driving circuit for a semiconductor apparatus includes a driver block 100, a multiplexer 200, and a control unit 300.
A driver block 100 includes a pull-up driver block 110 and a pull-down driver block 120.
A multiplexer 200 can receive clock signals (RCLKDO) and (FCLKDO) and parallel 2-bit data (RDO) and (FDO), and output serial one-bit data (UPDO) and (DNDO). A control unit 300 can receive a driver off signal (DOFF), an on-die termination enable signal (ODTEN), and a code signal (EMRS) output from an extended mode register set EMRS in order to determine driver strength, that is, an impedance. In response, the control unit can output driver selection signals (PU<0:3>) and (PD<0:3>). As shown in FIG. 2, a pull-up driver block 110 includes four pull-up drivers PU60Ω, PU120Ω, PU240Ω, and PU240Ω. Each of the four pull-up drivers PU60Ω, PU120Ω, PU240Ω, and PU240Ω includes a pre-driver PDRV and a main driver MDRV.
A pre-driver PDRV of the pull-up driver PU60Ω receives a one-bit serial data signal (UPDO), the driver selection signal (PU<3>), and the on-die termination codes (PCODE<0:5>). PDRV then outputs control codes (UPCODE3<0:5>). The main driver MDRV of the pull-up driver PU60Ωincludes a plurality of transistors, each having a source connected to a power supply terminal and a gate to which the control code (UPCODE3<0:5>) is input, and a plurality of resistors.
One end of each of a plurality of resistors is connected to the drain of the corresponding transistor, and the other end of each of resistors is connected to a common terminal. In one embodiment, the pull-up drivers PU120Ω and PU240Ω have the same structure as the pull-up driver PU60Ω, but when the impedances of the pull-up drivers are different from each other, the transistors have different widths and the resistors have different resistance values in the main drivers MDRV of the pull-up drivers.
The resistance values of the resistors forming the main driver MDRV increase proportional to impedance, and the widths of the transistors decrease inversely proportional to impedance. For example, as shown in FIG. 2, the resistance value of the pull-up driver PU120Ω is two times greater than that of the pull-up driver PU60Ω, and the width of the transistor in the pull-up driver PU120Ω is half the width of the transistor in the pull-up drivers PU60Ω. The resistance value of the pull-up driver PU240Ω is two times greater than that of the pull-up driver PU120Ω, and the width of the transistor in the pull-up driver PU240Ω is half the width of the transistor in the pull-up drivers PU120Ω.
For reference, a transistor WP has a reference width, and a transistor WP/8 has a width that is one-eighth of the reference width of the transistor WP. A transistor WP*16 has a width that is 16 times larger than the reference width of the transistor WP. A resistor RP has a reference resistance value, and a resistor RP*128 has a resistance value that is 128 times greater than the reference resistance value of the resistor RP.
As shown in FIG. 3, a conventional pull-down driver block 120 includes four pull-down drivers PD60Ω, PD120Ω, PD240Ω, and PD240Ω. Each of the four pull-down drivers PD60Ω, PD120Ω, PD240Ω, and PD240Ω includes a set of a pre-driver PDRV and a main driver MDRV.
A pre-driver PDRV of the pull-down driver PD60Ω receives one-bit serial data (DNDO), a driver selection signal (PD<3>), and on-die termination codes (NCODE<0:5>), and outputs control codes (DNCODE3<0:5>). A main driver MDRV of the pull-down driver PD60Ω can include a plurality of transistors, each having a source connected to a ground terminal and a gate to which the control code (DNCODE3<0:5>) is input, and a plurality of resistors. One end of each resistor is connected to the drain of the corresponding transistor, and the other end each resistor is connected to a common terminal.
The pull-down drivers PD120Ω and PD240Ω, in this embodiment, have the same structure as the pull-down driver PD60Ω. However if the impedances of the pull-down drivers are different from each other, the transistors have different widths and the resistors have different resistance values in the main drivers MDRV of the pull-down drivers. That is, the structural principle of the pull-down drives is the same as that of the pull-up drives shown in FIG. 2. For instance, a transistor WN has a reference width, and a transistor WN/8 has a width that is one-eighth of the reference width of the transistor WN. A transistor WN*16 has a width that is 16 times larger than the reference width of the transistor WN. A resistor RN has a reference resistance value, and a resistor RN*128 has a resistance value that is 128 times greater than the reference resistance value of the resistor RN.
A conventional multiplexer 200 converts parallel 2-bit data (RDO) and (FDO) into serial one-bit data (UPDO) and (DNDO) according to clock signals (RCLKDO) and (FCLKDO), and outputs the converted data. The extended mode register set EMRS outputs a code signal (EMRS) for determining the strength of the driver block 100.
A conventional control unit 300 determines the operation mode of the driver block 100 on the basis of the on-die termination enable signal (ODTEN) and the driver off signal (DOFF), and outputs the driver selection signals (PU<0:3>) and (PD<0:3>) according to the operation mode.
When a data input operation is performed in a conventional semiconductor apparatus, the driver off signal (DOFF) is deactivated, and the on-die termination enable signal (ODTEN) is activated. Then, the control unit 300 activates only the driver selection signals (PU<0:3>) among the driver selection signals (PU<0:3>) and (PD<0:3>) to control the driver block 100 to perform an on-die termination operation, thereby operating only the pull-up driver block 110 of the driver block 100.
The on-die termination strength, that is, the impedance of the driver block 100 is determined by the on-die termination codes (PCODE<0:5>) and (NCODE<0:5>).
When a data output operation is performed in such a semiconductor apparatus, both the driver off signal (DOFF) and the on-die termination enable signal (ODTEN) are deactivated. Then, the control unit 300 activates all of the driver selection signals (PU<0:3>) and (PD<0:3>) to control the driver block 100 to perform the data output operation, thereby operating both the pull-up driver block 110 and the pull-down driver block 120 of the driver block 100.
The driving impedances of the pull-up driver block 110 and the pull-down driver block 120 of the driver block 100 are determined by the driver selection signals (PU<0:3>) and (PD<0:3>) output from the control unit 300. The driver block 100 drives the data (UPDO) and (DNDO) according to the determined impedance, and outputs the data.
For example, the four pull-up drivers PU60Ω, PU120Ω, PU240Ω, and PU240Ω are all enabled in order to obtain a strength of 30 Ω. When the four pull-up drivers PU60Ω, PU120Ω, PU240Ω, and PU240Ω are all enabled, a resultant impedance of 30 Ω (1/( 1/60+ 1/120+ 1/240+ 1/240)=240/8=30Ω) is obtained by using an equation for calculating parallel resistance.
For example, the pull-up drivers PU60Ω and PU120Ω among the four pull-up drivers PU60Ω, PU120Ω, PU240Ω, and PU240Ω are enabled in order to obtain a strength of 40 Ω. When the pull-up drivers PU60Ω and PU120Ω are enabled, a resultant impedance of 40 Ω (1/( 1/60+ 1/120)=120/3=40 Ω) is obtained by using the equation for calculating parallel resistance.
When neither the data input operation nor the data output operation is performed in the semiconductor apparatus, the driver off signal (DOFF) is activated, and the on-die termination enable signal (ODTEN) is deactivated. Then, the control unit 300 deactivates all of the driver selection signals (PU<0:3>) and (PD<0:3>) to turn off both the pull-up driver block 110 and the pull-down driver block 120 in the driver block 100.
As described above, the data output driving circuit of the semiconductor apparatus requires many drivers in order to achieve various driving strengths and on-die termination strengths. In particular, since the 120-ohm and 240-ohm drivers have larger areas than the 60-ohm driver, the ratio of the area of the data output driving circuit to the area of the semiconductor apparatus increases. This results in a reduction in the layout margin.